The story
Blend of nephew or niece + sibling, coined by the American linguist Samuel Elmo Martin (1924–2009) in 1951.
First known use, by meaning
- from 1951 Used especially as a gender-neutral term: the child of one's sibling or sibling-in-law; one's nephew or niece.
Etymology from Wiktionary, CC BY-SA 4.0.